1. Field of the Invention
The present invention relates to a pressure sensing semiconductor device comprising a semiconductor chip which has a diaphragm formed with piezoresistance.
2. Description of the Background Art
FIG. 6 is a cross-sectional view showing the structure of a pressure sensing element 50 for use in conventional pressure sensing semiconductor devices. A semiconductor chip 101 includes a supporting part 101a and a diaphragm 101b. Piezoresistance 102 is located in the upper surface of the diaphragm 101b and surface electrode 103 are located on the upper surface of the supporting part 101a. 
The supporting part 101a of the semiconductor chip 101 is fixed on the upper surface of a seating 104. The seating 104 has a through hole 105 formed under the diaphragm 101b and is fixed on a metal package 106. The metal package 106 has a through hole 107 leading to the through hole 105 in the seating 104. On the rear surface of the metal package 106, a pressure leading-in tube 108 is provided which defines a through hole 113 leading to the through hole 107 in the metal package 106. The metal package 106 also has leads 109 which are electrically connected by fine Au wires 110 to the surface electrodes 103 on the semiconductor chip 101. The upper surface of the semiconductor chip 101 is coated with a moisture-proof resin 112 to cover the surface electrodes 103 and the Au wires 110. Further, a metal cap 111 is welded to the metal package 106 to cover the semiconductor chip 101 together with the metal package 106.
Although the pressure sensing element 50 shown in FIG. 6 is a pressure sensor designed to detect absolute pressure, it may be a pressure sensor designed to detect pressure relative to atmospheric pressure by forming holes to open up atmosphere in the metal cap 111.
FIG. 7 is a cross-sectional view showing the structure of a conventional pressure sensing semiconductor device. The pressure sensing element 50 shown in FIG. 6 is mounted on a printed circuit board 120. A control circuit component 121 for controlling the semiconductor chip 101 is further mounted on the printed circuit board 120 together with other circuit components such as a capacitor and a chip resistor. Further, a connector electrode 122 is soldered onto the printed circuit board 120 to establish electrical connections between the pressure sensing semiconductor device and external circuits. The control circuit component 121 and the connector electrode 122 are electrically connected to the leads 109 in the pressure sensing element 50. Also, a metal shielding case 123 is soldered onto the printed circuit board 120 to cover the pressure sensing element 50. The printed circuit board 120 and the metal shielding case 123 are surrounded by resin cases 124, 125 in the shape of connectors leading to external circuits.
Since such a conventional pressure sensing semiconductor device requires, in addition to the pressure sensing element 50, the printed circuit board 120, the metal shielding case 123, the resin cases 124, 125, and the like, it was difficult to do miniaturization of the device and to simplify the assembling process.
In addition, a limited space between the rear surface of the printed circuit board 120 and the resin case 125 prevents another metal shielding case 123 from being provided on the rear surface side of the printed circuit board 120, and therefore especially the control circuit component 121 has low EMI tolerance.
A first aspect of the present invention is directed to a pressure sensing semiconductor device comprising: a semiconductor chip having a diaphragm formed with piezoresistance; a seating having a first main surface to which the semiconductor chip is fixed and in which a through hole is located at a point facing the diaphragm; a pressure leading-in tube of metal having a cylinder leading to the through hole in the seating and a flange having a first main surface fixed to a second main surface of the seating on the opposite side of the first main surface of the seating; and a metal substrate having a through hole in which the cylinder is inserted and a control circuit electrically connected to the semiconductor chip, the metal substrate being jointed to the flange by welding.
A second aspect of the present invention is directed to a pressure sensing semiconductor device comprising: a semiconductor chip having a diaphragm formed with piezoresistance; a seating having a first main surface to which the semiconductor chip is fixed and in which a through hole is located at a point facing the diaphragm; a pressure leading-in tube of metal having a cylinder leading to the through hole in the seating and a flange having a first main surface fixed to a second main surface of the seating on the opposite side of the first main surface of the seating; and a metal substrate having a through hole in which the cylinder is inserted, a control circuit electrically connected to the semiconductor chip, and a conductive pattern formed on a main surface facing the flange, the metal substrate being jointed to the flange by soldering the conductive pattern to a second main surface of the flange on the opposite side of the first main surface of the flange.
According to a third aspect of the present invention, in the device of the second aspect, at least either of the second main surface of the flange and a surface of the conductive pattern is plated to improve joint adhesion.
According to a fourth aspect of the present invention, the device of either of the first to third aspects further comprises: a metal cover fixed on the metal substrate to cover the semiconductor chip and the control circuit together with the metal substrate.
According to a fifth aspect of the present invention, the device of either of the first to fourth aspects further comprises: a glass cap fixed on the semiconductor chip and having a closed chamber to form a pressure standardized chamber on the diaphragm.
According to a sixth aspect of the present invention, in the device of either of the first to fifth aspects, the metal substrate further includes: a mounting part for mounting the pressure sensing semiconductor device to a target; and a connector electrode for establishing electrical connections between the pressure sensing semiconductor device and an external circuit.
A seventh aspect of the present invention is directed to a pressure sensing semiconductor device comprising: a semiconductor chip having a diaphragm formed with piezoresistance; a seating which has a through hole facing the diaphragm and to which the semiconductor chip is fixed; a pressure leading-in tube leading to the through hole; a substrate having a control circuit electrically connected to the semiconductor chip; and a glass cap disposed on the semiconductor chip and having a closed chamber to form a pressure standardized chamber on the diaphragm.
In accordance with the first aspect, the device can be miniaturized since none of the conventional metal package and resin cases is required.
In accordance with the second aspect, the device can be miniaturized since none of the conventional metal package and resin cases is required.
The device of the third aspect can improve joint adhesion of the metal substrate to the flange.
The device of the fourth aspect can improve EMI tolerance since the cover and the metal substrate are at the same potential.
The device of the fifth aspect permits single wafer processing in forming the glass cap, thereby improving productivity.
In accordance with the sixth aspect, the device can further be miniaturized.
The device of the seventh aspect permits single wafer processing in forming the glass cap, thereby improving productivity.
An object of the present invention is to provide a down-sized pressure sensing semiconductor device with improved EMI tolerance as compared with conventional ones.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.